1. Field of the Invention
The present invention is related to movable barrier operators and more particularly, to the control of a motor for driving a movable barrier such as a garage door.
2. Background Description
Movable barrier operators and, more particularly, garage door operators are well known and have become very sophisticated to provide users with increased convenience and security. Such barrier movement operators may move barriers such as gates and garage doors which have a relatively large mass which brings into play a relatively large inertia. In order to overcome such inertia electric motors of significant power are used to move the barrier. Thus, a system exists in which an object of relatively large inertia is being powered by a motor of relatively large power. Barrier operator safety is achieved by providing a plurality of sensors to the operation of the barrier and a control method which stop or reverse barrier movement according to the condition sensed.
It is common for barrier operators to employ A.C. induction motors to power barrier movement. Such motors include some arrangement of switched start windings and/or switched capacitors to urge the motor into rotation in a selected direction. When a barrier is being moved in a first direction and a safety condition is sensed, known arrangements rapidly enable the starting of motor rotation to reverse direction of the barrier. Such enabling may be constant or it may be pulsed to first slow the barrier then cause it to reverse direction.
Reversing the direction of barrier movement by beginning a reverse motor starting process creates noise and vibration from the motor. The noise, by itself is an annoyance to those nearby while the vibration may shorten the life of the barrier and operator system. A need exists for improved methods and apparatus for reversing the direction of barrier travel in a barrier operator system.
The present invention provides a plurality of motor reversal algorithms and selects one of the algorithms for use depending on the type of reversal need sensed. The actual rotation speed of the motor may be sensed and be used to decide which algorithm to use and/or how a selected algorithm is to be employed. For example, when the sensed need indicates that the barrier may be contacting an obstruction, a relatively rapid reversal may be attempted. For protection of property and other reasons, the increased vibrations may be tolerated. The rapid reversal may be moderated by the sensed RPM during the reversal process. Also, for example, when a sensed reversal condition does not indicate actual contact (called non-contact) a second algorithm which allows a longer time to complete the reversal may be used. The second algorithm reduces the noise and harmful vibrations of immediate reversal and may also be moderated by sensed motor RPM during the reversal process.